Sequence of Operation
94
OAU-SVX01K-EN
Condensate Detection Input will display a fault when the
switch located in the condensate pan for the indoor coil
has tripped.
Emergency Stop will display a fault if the Emergency Stop
circuit is opened. Line 76 on the wiring diagram shows the
circuit to energize the Emergency Stop Relays.
The unit is shut down when this diagnostic occurs,
including the supply fan.
Compressor Low Ambient Lockout Active will display a
fault if there is a demand for cooling according to the
setpoints, but the Outdoor Air Temperature Active is
below the Compressor Low Ambient Lockout Setpoint and
the unit does not have active head pressure control.
These diagnostic locks out compressor operation.
Diagnostic: Compressor [1, 2,...] Run Failure is displayed
when there is a command for a compressor but there is no
active status for the compressor. Compressor status is
indicated using the NC contact on the compressor
auxiliary contactor.
Upon an initial call for a compressor, there is a five minute
and thirty second delay of no run status before an alarm is
indicated. If there is five minutes of continuous operation
with the run status, there is a thirty second delay before the
alarm is displayed.
The program will disable the output for that compressor if
there is run status alarm indicated. The diagnostic is
cleared when there is an alarm reset or the diagnostic has
been active for 3 hours.
Diagnostic: Compressor Fail Unit Lockout is displayed
when there is a run failure diagnostic for one of the
compressors and the unit is supplying unsatisfactory
conditions for ten minutes. Unsatisfactory conditions are
identified by the Discharge Air Temperature Local is 2°F
above or below the Discharge Air Temperature Setpoint
Active during Heat Pump Heating or Cooling Mode, or
when the Dehumidification Temperature Active is 2°F
below the Dehumidification Temperature Setpoint Active
during Dehumidification Mode.
The unit is shut down when this diagnostic occurs,
including the supply fan. The diagnostic can be cleared
with an alarm reset and will auto-reset once the
compressor run failure diagnostic is cleared.
Diagnostic: Condensate Overflow Unit Lockout is
displayed when the Condensate Detection Input has
failed, and the unit is supplying unsatisfactory conditions
for five minutes. The unsatisfactory conditions use the
same criteria as the Diagnostic: Compressor Fail Unit
Lockout.
The unit is shut down when this diagnostic occurs,
including the supply fan. The diagnostic will auto-reset
five minutes after the condensate diagnostic has cleared.
Diagnostic: Heat Failure is displayed after three failed
attempts to ignite the primary indirect fired gas heater
within a four-hour period. The unit is shut down when this
diagnostic occurs, including the supply fan
Diagnostic: [High, Low] Discharge Air Temp Lockout is
displayed when the Discharge Air Temperature Local is
[above 128°F, below 35°F] for a duration of 10 minutes. The
diagnostic is manual reset using Alarm Reset.
Diagnostic: Liquid Line Refrigerant Pressure Circuit [1,2]
Source Failure is displayed when the respective circuit is
on (indicated by the compressor run status) and the Liquid
Line Refrigerant Pressure Circuit [1,2] falls outside of the
range of 150-650 PSI for a duration of two minutes. When
this occurs, the condenser fans will run at 100%
Diagnostic: Low Outdoor Coil Water Flow is displayed if
the supply fan is running but the Outdoor Coil Water Flow
Status indicates that there is no flow for 20-seconds. The
compressors will be prevented from operating when this
diagnostic occurs and will auto-reset once the flow
returns.
The Outdoor Coil Water Flow Status is indicated using a
differential pressure switch across the inlet and outlet of
the water coils.
Diagnostic: Outdoor Coil Water Temperature Low is
displayed if the supply fan is running but the Outdoor Coil
Water Low Temperature Switch indicates that the water
temperature is too low. The compressors will be
prevented from operating when this diagnostic occurs and
will auto-reset once the temperature switch closes.
The temperature switch is located on the water return and
the switch opens at 35°F for water, 20°F for glycol
Diagnostic: Low Refrigerant Suction Pressure Circuit [1,2]
is displayed when the respective circuit is on (indicated by
the compressor run status) and the Suction Line
Refrigerant Pressure Circuit [1,2] Local falls below 85 PSI
(55 PSI for heat pump heating) for two continuous
minutes. The diagnostic auto clears when the pressure
returns to normal.
Diagnostic: Outdoor Air Damper End Switch is displayed
when Outdoor Air Damper Open Close Command is On,
but the Outdoor Air Damper End Switch does not prove for
3-minutes. The diagnostic is reset using Alarm Reset or
when the end switch is proven.
Diagnostic: Return Duct/Space Pressure Setpoint Range
is displayed when the Return Duct/Space Pressure
Setpoint is set within 20% of the maximum limit of the
Return Duct/Space Pressure Local. If the setpoint is set too
close to the maximum range of the sensor, it will not be
able to recognize when it’s outside of the operating range.
Diagnostic: Duct Static Pressure Setpoint Range is
displayed when the Duct Static Pressure Setpoint BAS is
set within 20% of the maximum limit of the Duct Static
Pressure Local. If the setpoint is set too close to the
maximum range of the sensor, it will not be able to
recognize when it’s outside of the operating range.
Diagnostic: Supply Fan Failure is displayed when the
Supply Fan Start Stop Command is On, but the Supply Fan
Status does not prove for two minutes. The diagnostic
requires a manual reset using Alarm Reset.
